Shot blasting apparatus



1944. w. J. LEARMONTH 2,338,591

SHOT BLASTING APPARATUS Filed Nov. 17, 1941 2 Sheets-Sheet 1 ATTORNEYS Jan. 4, 1944.

w. .1. LEARM ONTH SHOT BLASTING APPARATUS Filed Nov. 17, 1941 2 Sheets-Sheet 2 by W 41/ ATTORNEYS Patented Jan. 4, 1944 UNITED STATES PATENT OFFICE signor to The Studebaker Corporation, South Bend, Ind., a corporation of Delaware Application November 17, 1941, Serial No. 419,411

Claims.

The present invention relates to an improvement in an apparatus for shot blasting metal articles, and more particularly is directed to an apparatus for shot blasting spring leaves.

It is now well known in the art that by shot blasting a spring leaf its life and resiliency are greatly increased. In order to satisfactorily shot blast a leaf spring, for example, the shot must be discharged so that it impinges the leaf spring with great force. This immediately creates a serious and dangerous problem. The blast of shot must be confined to prevent injuries to the workman, and hence necessarily requires that the shot blasting be accomplished within a closed housing. In apparatus now known in the art the force of the shot will, in a relatively short time, puncture the wall of the housing necessitating a shutting down of the apparatus for repair. Further, the shot, due to the force imparted to it, will be expelled from the discharge end of the housing and, in addition, will lodge in the links of the conveyor and about the sprockets over which the conveyor chain is trained. The shot is of an abrasive character and a conveyor chain and sprocket will be damaged beyond the point of usefulness in a short time, necessitating their replacement. This is objectionabl in that in addition to shutting down the apparatus for repair, the conveyor chain and sprockets are costly to replace.

The primary object of my invention is to provide an improved shot blasting apparatus which is safe and economical in operation.

A further object is the provision of means for preventing damage to the conveyor and housing by the shot.

A further object is to provide a shot blasting apparatus in which substantially all of the shot will be retained within the housing.

In order to attain the above objects, I propose to provide a resilient shock absorbing covering for the conveyor chain to protect it from discharging shot. Further, I propose to line the inner surfaces of the housing of the apparatus with suitable resilient shock absorbing material to prevent the shot from wearing through and destroying the walls of the housing.

Preferably, suitable means is provided adjacent the discharge end of the housing or the apparatus for retaining the shot within the housing.

A specific feature of my invention resides in providing a slot in the track for the conveyor adjacent the outlet of the housing into which the shot accumulated between thelinks of the conveyor will drop to be expelled into a suitable receptacle and returned to a feed hopper for further use.

A further feature of my invention resides in the provision of a guide means adjacent the discharge outlet of the housing for assuring that objects being shot blasted will not jam the machine.

Now, in order to acquaint those skilled in the art with the manner of constructing and operating an apparatus of my invention I shall describe in connection with the accompanying drawings a preferred embodiment of the invention.

In the drawings:

Figure l is a side elevational view, largely diagrammatic, of an apparatus embodying my invention;

Figure 2 is an enlarged detail plan view of a portion of the conveyor chain;

Figure 3 is a side elevational view of the chain of Figure 2;

Figure 4 is a detail vertical sectional view taken substantially on the line 4-4 of Figure 3 and looking in the direction indicated by the arrows;

Figure 5 is a plan view, partly in section, of the housing and a portion of the conveyor chain shown in Figure l;

Figure 6 is a detail vertical view taken substantially on the line 66 of Figure 5 and looking in the direction indicated by the arrows;

Figure '7 is an enlarged plan view of a portion of the conveyor track, showing in section a portion of the outlet end of the shot blasting housing, and of the means for directing an air stream inwardly of the discharge outlet of the housing;

Figure 8 is a detail sectional View taken sub stantially along the line 8-8 of Figure '7, looking in the direction of the arrow; and

Figure 9 is an enlarged detail view taken substantially on the line 9-9 of Figure 6 and showing the guide means for guiding a leaf spring out of the outlet end of the apparatus.

Referring now to Figure l, the apparatus therein shown comprises a housing H, and an endless conveyor chain l2 which is adapted to be trained about a pair of sprockets l3. Suitable driving means 14 is disposed adjacent the sprockets l3, at, the left of Figure 1, for driving the conveyor chain in a counterclockwise direction as viewed in the figure. Disposed above the housing H is a suitable feed chamber or hopper Iii for storing the shot which is adapted to be discharged by a suitable centrifugal discharge means it which may be driven by any suitable means (not shown). It will be understood that the reextending through a suitable lug 43.

cep'tacle l and shot-discharging means [6 are well known in the art and for the purposes of the present invention need not be described in further detail.

Suitable inspection doors l9 are provided, one in each of the side walls of the housing I I. A receptacle 2? is disposed below the housing H for receiving the spent shot. A pair'of idler sprockets 2l-Zl are disposed adjacent the lower end of the receptacle 2i] for guiding the conveyor chain along its lower turn. The housing I I also comprises a reduced outlet portion 22 which will be described in more detail hereinafter. The pair of sprockets l3 are disposed a sufiicient distance away from each end of the housing I I to provide loading and unloading stations for objects to be treated in the housing. The sprockets l3 are each carried by a suitable supporting platform 24 so that the upper link of the chain is disposed substantially at waist height.

In the embodiment of my invention herein disclosed I have shown in several figures of drawings an apparatus suitable for shot blasting leaf springs. The leaf springs shown at 25 are adapted to be disposed upon the conveyor chain I2 at the right hand end of the machine as shown in Figure 1, and after passing through the housing H wherein they are shot blasted, they are removed at the left hand end of the apparatus shown in this figure.

The track 21 extends longitudinally through the housing II and terminates adjacent each of the sprockets I3 which are suitably supported at either end of the apparatus by the frame members 24.

Referring now to Figures 2 through 4, it will be seen that the conveyor chain I 2 comprises a plurality of outer links-35 and a plurality of inner links 35, the inner and outer links being pivotally connected to each other adjacent their ends. A plurality of rollers 32 are disposed between each pair of inner links 3|, and are mounted for rotation about the axis of a pin 33 which connects the ends of adjacent pairs of linksti! and 3!. Each of the links are provided with suitable lugs-M to which are secured metal plate members 35 by means of the nuts and bolts 31. A leaf spring supporting member's!) is adapted to be detachablysecured to each of the plate Disposed adjacent each end of each members 35. of the plate members 4!] are a pair of lug members H which are adapted to be disposed in en-- gagement with a tapered shoulder ofthe plate member 35. The opposite side of each of the plate-members ii) is-provided with a screw 32 The screw :22 is adapted to have engagement with a tapered edge of the plate member 35 for holding the several members ll in engagement with the opposite tapered edge of the plate 35 to retain the several plate members 48 in assembled position upon the conveyor chain.

A pair of pins 50 are disposed substantially midwayof and opposite each of the plate members 5d, and at each side thereof. One end of each of the pins 5i! are threaded for securing them in suitablythreaded openings in the plate members til. A suitable partition.52,,preferably ..of metal, extends upwardly from the plate member ii) to which it may be suitably secured as; by,

welding. A pair of resilient shock absorbing coverings 53 are providedv on either side of the partition 52, and the upper edge of the, partition 52 is also provided with asuitable resilientishock absorbing covering; 54,

In Figures 2 and 3, it Will be seen that in the embodiment herein disclosed that each third link is provided with a work supporting member 40 and covering therefore as described in connection With Figure 4. It will be seen that the link structures intermediate the Work supporting links each comprise a transversely extending metal bar 55 secured to the lugs 34 of the outer pairs of links as. The several platev members 55 are suitably secured as by bolting to their associated lugs 35. A covering 51 of a resilient shock absorbing material is secured to the transverse members -55 in any suitable manner to protect the several intermediate links of the chain from the discharging. shot. Preferably, the resilient coverings 53, thecoverings 54 and the coverings 51 are of soft rubber, but it will be apparent that they may be made of any other suitable material of like character.

In Figures 5 and 6 it will be seen that the housingll comprises a first or inlet compartment 60, a second or shot blasting compartment-"Bl, a third compartment 82, and an outlet or discharge compartment 84. A suitable guideway --comprising side Walls '66 and a top wall 61 define a guiding means through which articles to be 'shot blasted are carriedby the conveyor I2. A plurality of bifurcated rubber sheeting members extend substantially vertically within the guide 68 to prevent shot from being discharged outwardly of the guide 55. Adjacent the inner end of the member 65am a pair of plate members 10 which extend inwardly from the outer walls 66 toward the conveyor chain and terminate adjacent the end wallf12 defining the inlet end of the chainberti.

.In' the embodiment of the invention herein disclosed, a plurality of leaf springs 15 are'adapted to be disposed upon the conveyor chain bypositioning a suitable opening formed substantially intermediate the ends of each of the springs 15 about each of the pins 50 of each of the work supporting members 4!].

In Figure 6 it will be seen that the shot discharging means comprises the centrifugal Wheel 16 for directing shot downwardly upon the leaf springs as they pass through the chamber 6|. The tapering inner end Walls 10 of the housing are adapted to aline the several leaf springs i5 as they approach the shot blasting housingBl and as shown in Figure '6 it will be seen that the eye of the spring is guided by the upper wall 61 for guiding the spring from the housing 65 into the shot blasting chamber iii. The inner. sur- 'faces of the end wall'12 of the chamber'fil, .and

the end. wall 18 adjacent the outlet of the chamber 6| are each provided with a layer of resilient shock absorbing material 19 for absorbing the shock of the shot .thrownthereagainst by the shot discharging meansv 13. Also, the inner side walls 8i] of the chamber 6| are. provided with suitablecoverings of resilient shock absorbing material 8!. The inner surfaces of the. inspection doors opening into. the shot blasting chambers 6! are also provided with .a.-suitable layer of shock absorbing material 82. The.shock.ab sorbing material shown at 15, SI and 82, preferably comprises soft rubber. If desired, other material of like character may be used.

From the above it-Will be clear that'all exposed surfaces of the walls defining the chamber BI, and all exposedsurfaces of the conveyorchain areprovided with suitable shock absorbingcoat- :ings toprevent the dischargingshot from.im-

pinging directly on any metal parts except the leaf springs being treated.

The outlet compartment 64 of the housing H comprises a plurality of vertically extending sheet members 84, preferably bifurcated sheet rubber, which partially prevent the expulsion of shot from this end of the apparatus. It will be seen that the conveyor track adjacent one end of the housing 65 is provided with a diagonally extending slot 85 into which shot accumulated by the wheeled links of the conveyor chain are dropped. A pair of conduits 86 and 81 extend from either side of the housing 64 adjacent the outlet end thereof and are provided with tips 38 which extend inwardly of the housing 64. The conduits 86 and 81 are connected to any suitable source of air under pressure, and the tips 88 and 89 are directed to discharge an air stream adjacent either side of the track inwardly of the apparatus. These air streams are effective to retain the spent shot within the apparatus and cause it to be returned to the receptacle 20 from which it is conveyed by any suitable means, such as bucket conveyors, to the supply chamber 15 to again be used. It will be seen that the discharge tip 89 of the conduit 8'! lies substantially in alinement with the groove 85 f the track so that a blast of air is directed through this slot to return to the hopper 2i] spent shot accumulated therein.

Disposed adjacent the upper wall and suitably secured thereto is a guide trough I00 shown in detail in Figure 9. The guide member I00 comprises a pair of downwardly extending flanges Hll which converge toward each other adjacent the outlet over the compartment 64. In the position of the forwardmost spring 15 shown in Figure 6 it will be seen that shot is being directed upon the trailing end thereof which tends to rock the spring about the pin 50 as a fulcrum and unless a guide of the character of I00 is embodied in the upper end of the compartment 64 the leading end of the spring will bind in the apparatus and cause serious damage and delay. The converging flange of I01 serves to guide the leading ends of the springs out of the housing II. A suitable lug I02 preferably formed integral with the guide member I00 extends downwardly and inwardly of the compartment 64. The lug I02 is provided with a suitable opening at I03 for receiving a discharge nozzle 104 Of a suitable conduit I95 which is connected to a source of air under pressure for discharging a stream of air inwardly and downwardly of the compartment 64 to drive spent shot back into the apparatus and into the hopper 20 which would otherwise be carried out of the housing. A suitable valve I06 may, if desired, be incorporated in the conduit I for regulating or shutting off the flow of air through the nozzle I04.

It will be understood that the shot discharging wheel 16 is of a type well known in the art and comprises a discharge recess or slot H0 which is in communication with the discharge end of the hopper for discharging the shot within the compartment 8|. Also, devices of the character referred to comprise a plurality of removable baffles III to aid in guiding the shot upon the articles being treated.

Also, it will be understood that a suitable screw conveyor extends from the lower portion of the hopper for returning the spent shot to a suitable elevating means for returning it to the feed hopper 15. These several elements have only been illustrated diagrammatically in elevation since they are well known in the art.

While I have shown what I consider to be the preferred embodiment of my invention, it will be understood that various modifications and rearrangements may be made therein without departing from the spirit and scope of the invention.

I claim:

1. In an apparatus of the character described, the combination of a housing, means for discharging shot in said housing, an endless wheeled conveyor for conducting objects to be shot blasted through said housing, a track upon which the wheels of said conveyor are adapted to travel having a slot therein adjacent the discharge end of said housing, and means for directing an air stream through said slot inwardly of said housing.

2. In an apparatus of the character described, the combination of a housing, means for discharing shot in said housing, an endless conveyor comprising a plurality of pivoted wheeled links, a track for said conveyor extending through said housing, said track having a slot for receiving spent shot accumulated by said wheeled links, a receptacle for receiving the spent shot, and means for directing an air stream adjacent the outlet end of said housing for returning spent shot into said receptacle, said means being adapted to direct an air stream through the slot of said track for forcing the spent shot therein into said receptacle.

3. In an apparatus of the character described. the combination of a housing, means for discharging shot in said housing, an endless conveyor comprising a plurality of pivoted wheeled links, a track for said conveyor extending through said housing, said track having a slot for receiving spent shot accumulated by said wheeled links in passing through said housing, means for directing air streams inwardly of the housing and into the discharge end thereof and adjacent each side of the conveyor, one of said air streams being adapted to expel the spent shot in the slot in said track, and means for directing the air stream from above said conveyor downwardly and inwardly of the housing from the discharge end thereof.

4. In an apparatus of the character described, the combination of a housing, means for discharging shot in said housing, an endless conveyor for conducting objects to be shot blasted through said housing, guide means adjacent the discharge end of said housing for engaging the leading portions of the objects while the rear portions thereof are being shot blasted to guide the same outwardly of said housing, and means carried by said guide means for directing an air stream inwardly of said housing.

5. In an apparatus of the character described, the combination of a housing, means for discharging shot in said housing, endless conveyor for conducting objects to be shot blasted through said housing lengthwise thereof, and a guide trough extending lengthwise of said housing adjent the discharge end thereof, said guide trough comprising sidewalls converging toward each other adjacent the discharge end of said housing for engaging the objects being shot blasted to retain them in their lengthwise positions at the discharge end of said housing.

WILLIAM J, LEARMONTH- 

